A characteristic which a lubricating oil for automobiles and industrial machines has heretofore been required to have is, for example, a relatively high viscosity in terms of lubricating performance. However, in consideration of an environment conservation for which there are growing concerns in recent years, a further reduction in fuel consumption, further energy savings, and an increase in lifetime have been demanded, and hence a synthetic lubricating oil having a more excellent viscosity characteristic (higher viscosity index), a more excellent low-temperature characteristic (low-temperature flowability), and more excellent oxidation stability than those of a poly-α-olefin that has heretofore been used has been demanded. A conventional hydrocarbon-based synthetic lubricating oil is obtained by, for example, a method involving polymerizing 1-decene, or 1-decene and 1-dodecene, through the use of aluminum chloride or aluminum bromide as a catalyst (Patent Literature 1). However, the viscosity index, pour point, and durability of the resultant α-olefin polymer have not been sufficient.
In recent years, an attempt has been made to produce a high-performance α-olefin (co)polymer with a metallocene catalyst, and it has been known that an α-olefin copolymer having an excellent viscosity characteristic, an excellent low-temperature characteristic, and excellent durability is obtained (Patent Literatures 2 to 14).